Preparation of glyoxylic acid

ABSTRACT

Glyoxylic acid is obtained by cathodic reduction of oxalic acid in the presence of a tertiary amine or a quaternary ammonium salt. The presence of the nitrogeneous compound allows efficient reduction to take place using a commercial unpurified oxalic acid.

United States Patent Michelet *Dec. 30, 1975 PREPARATION OF GLYOXYLIC ACID [75] Inventor: Daniel Michelet, Tassin La [56] References Cited Demi-Lune, France UNITED STATES PATENTS 815,548 3/1906 Mettler 204/75 [73] Assrgnee. Rhone Poulenc, S.A., Pans, France 3,755,101 8/1973 Rakoutz H Notice: The portion of the term of this 3,779,875 12/1973 Michelet 204/76 patent subsequent to Dec. 18, 1990, has been disclaimed. Primary Examiner-F. C. Edmundson Attorney, Agent, or Firm-Cushman, Darby & [22] Filed Nov. 30, 1973 Cushman [21] Appl. No.: 420,576

[57] ABSTRACT 30 Foreign Application priority Data Glyoxylic acid is obtained by cathodic reduction of Dec 1 1972 France 72 42836 oxalic acid m the presence of a tertiary amine or a quaternary ammonium salt. The presence of the ni- [52] CL 204/77 2O4/75 204/76 trogeneous compound allows efficient reduction to [51] Int I CZSB 3/04 take place using a commercial unpurified oxalic acid. [58] Field of Search 204/75, 76, 77; 260/535 R 10 Claims, N0 Drawings PREPARATION OF GLYOXYLIC ACID The present invention relates to a new process for the preparation of glyoxylic acid by cathodic reduction of oxalic acid.

U.S. Pat. Application Ser. No. 281,741 describes the use of certain nitrogen-containing adjuvants as additives to the catholyte in the preparation of glyoxylic acid by cathodic reduction of oxalic acid. These nitrogen-containing adjuvants make it possible:

a. to use commercial oxalic acid for the preparation of glyoxylic acid, without it being necessary to recrystallise it several times,

b. to use oxalic acid from the most diverse sources, without it being necessary either to subject them to any special purification treatment or to take special precautions as to the nature of the apparatus and the ions originating therefrom, and

c. to reduce the formation of hydrogen at the cathode in the electrolysis of oxalic acid, which makes itpossible to obtain better electrical yields (decrease in the electrical yields corresponding to the production of hydrogen).

The present invention involves the use of new nitrogen-containing adjuvants in the preparation of glyoxylic acid by cathodic reduction of oxalic acid.

The present invention provides a process for the preparation of glyoxylic acid by cathodic reduction of oxalic acid, by carrying out an electrolysis in an electrolyser comprising a cathode, a cathode compartment, a separating diaphragm, an anode and an anode compartment wherein the said cathode compartment containing a catholyte consisting essentially of an aqueous solution of oxalic acid and 0.00005 to 1% w/w of an adjuvant chosen from:

a. tertiary amines of the general formula b. ditertiary diamines of the general formula c. quaternary ammonium salts of the general formula and, d. quaternary ammonium salts of the general formula in which R R and R each represent a linear or branched, saturated or unsaturated, aliphatic hydrocarbon radi- 2 cal, or two of R R and R together represent a single saturated alkylene or oxydialkylene radical, or R R and R can each represent an aliphatic radical containing at least one oxyalkylene link, at least one of the readicals R R and R being an arylaliphatic radical, the'radicals R R and R together having less than 40 carbon atoms;

R ,R ,R and R each represent linear or branched saturated or unsaturated aliphatic hydrocarbon radicals, or an aliphatic radical containing at least one oxyalkylene links or at least one of R and R together or R and R together represent a single alkylene or oxydialkylene radical,

R represents an aliphatic or arylaliphatic, divalent hydrocarbon radical, the aliphatic chain or chains of which can be interrupted by oxygen atoms, the free valencies of the radical R being carried by aliphatic carbon atoms, and the total number of carbon atoms in the radicals R R R R and R being greater than 6 and less than 40;

R R R and R each represent a linear or branched, saturated or unsaturated, aliphatic hydrocarbon radical, or an aliphatic radical containing at least one oxyalkylene links, or two of R R R and R together form a single saturated alkylene or oxydialkylene radical,

at least one of R R R and R being a monova lent aromatic hydrocarbon radical which is either purely aromatic, or arylaliphatic, or aromatic and having as substituents saturated or unsaturated, linear or branched, aliphatic radicals, the total number of carbon atoms in R R R and R being more than 15 and less than 40;

R R R R R and R are as defined for R R R and R and R is as defined for R the total number of carbon atoms in R R R R R R and R being more than 8 and less than 40;

yis equal to 1,2or 3,and

A" is hydroxy or an anion such that AH represents an inorganic or organic acid.

When one of the R groups is one containing an oxyalkylene link, the R group may be one of formula (CH ),,[O(CH OH where n= 2 or 3 and m 1 to 10. The arylaliphatic group R R and/or R may be of formula C l-l R where R is a linear or branched saturated or unsaturated, aliphatic divalent hydrocarbon radical.

The precise nature of A" is not critical and such an anion can be replaced by another in accordance with the conventional techniques of ion exchange; as a possible value of A" in addition to the hydroxyl radical, there may be mentioned nitrates, sulphates, phosphates, sulphonates, bicarbonates, oxalates and halides, and especially chlorides, bromides and iodides.

The adjuvants used in the invention are essentially those which are soluble in water at the concentration considered, and in particular it is preferred to choose A" so as to achieve this solubility.

As adjuvants which can be used, there may be mentioned very especially:

tribenzylamine; (dimethylamino)-ethyl ether; dimethyl-benzyl-dodecyl-ammonium, diethyl-benzyldodecyl-ammonium, dimethyl-benzyl-tetradecylammonium, diethyl-benzyl-tetradecyl-ammonium, dimethyl-benzyl-hexadecyl-ammonium, diethyl-benzylhexadecyl-ammonium, dimethyl-benzyl-octadecylammonium, diethyl-benzyl-octadecyl-ammonium, dimethyl-benzyl-eicosyl-ammonium, diethyl-benzyLeico syl-,ammonium,, climethyl-benzyl-docosyl-ammonium and diethyl-benzyl-docosyl-ammonium hydroxidesand salts, especially halides; dimet hyl-phenyl-dodecyl-.

- especially dihalides.

The temperature of the catholyte is generally be tween and 70C, .and preferably between and C.

Metals which are capable of forming the cathodes of the process of the invention, include principally lead, cadmium, mercury and amalgams, as well as the alloys of these various metals, particularly with silver, tin and antimony. The anode of the electrolysis cells used in the invention consists, in practice, of a material which conducts electricity and which is electrochemically stable in the anolyte and under the working conditions considered. Materials which are thus suitable for forming the anode, include metals and metalloids such as platinum, platinised titanium, graphite and lead and its alloys, particularly with silver, antimony and tin.

The separating diaphragm between the anode and cathode compartments is preferably a cation exchange membrane. The nature of the latter is not characteristic of the invention; thus any known membrane can-be used, and in particular membranes of the homogeneous type and membranes of the heterogeneous type; these membranes can optionally be reinforced with a screen; for the purpose of being able to carry out electrolysis operations of long duration, it is naturally preferred to use membranes which do not swell and which are stable to the action of the various constituents of the catholyte and the anolyte. As membranes which can be used, there may mentioned more particularly those described in the following patents:

U.S.- Pat. No. 2,681,320 and France Pat. No. 1,568,994, 1,575,782, 1,578,019, 1,583,089, 1,585,187 and 2,040,950.

The permeation selectivity of the membranes used (measurement made as in French Pat. No. 1,584,187) is preferably greater than 60%.

Thecatholyte used in the process according to the invention comprises essentially:

water,

oxalic acid,

glyoxylic acid,

one or more adjuvants having one of the formulae 1 to 1V, and

optionally a strong inorganic acid such as sulphuric acid; however, it is preferred not to use such an acid.

The catholyte can contain oxalic acid without glyoxylic acid only at the start of electrolysis; in the same way, the catholyte can contain glyoxylic acid without oxalic acid only at the end of electrolysis. The concentrations of these oxalic and glyoxylic acids can be either constant when the reaction is carried out continuously, or variable when the reaction is carried out discontinuously or during the starting of a continuous operation. In all cases, the concentration of oxalic acid is less than the saturation value at the temperature considered; generally, this concentration is greater than 2% by weight; this value relates particularly to the constant concentration when the reaction is carried out continuously and to the final concentration when the reaction is carried out discontinuously. The concentration of' glyoxylic acid is usually between 3 and 25% by weight, and preferably between 5 and 15%-'by .weight,.these values relating particularly to the constant concentration of glyoxylic acid when thereaction is carried out continuously and to the final concentration of this same acid when the reaction is carried out discontinuously.

As has been indicated above, the concentration of adjuvant in the catholyte is 0.00005 to- 1% by weight. This concentration is preferably 0.0001 to 0.5%; the use of these small amounts has the value of making it possible to refrain from removing the adjuvant from the glyoxylic acid produced, as this adjuvant then exerts practically no harmful effect on the properties of the said acid. I

The catholyte can, optionally and in addition, contain reaction by-products in small amounts, generally less than 1%.

An aqueous acid solution is preferably used as the anolyte. The precise nature of thisanolyte is not characteristic of the invention because the purpose of the said anolyte is essentially to provide electrical conductivity between the two electrodes. Aqueous solutions of sulphuric or phosphoric acids are usually employed. The concentration of these solutions is generally between 0.1 and 5 mols/litre, and preferably between 0.5 and 2 mols/ litre.

The current density at the cathode is generally'3 to 50 A/dm andpreferably 10 to 35 A/dm.

In order to carry out the invention, electrolysersof any known type can be used, for example, those of the patents mentioned above and especially Belgian'Pat. No. 757,106. 3

However, it is preferred to employ electrolysers with solid electrodes, which makes it possible to produce compact apparatuses, especially of the filter press type. The electrodes and the separating diaphragm are ad'- vantageously arrang'ed in parallel plane's.

Also advantageously, the catholyte and the anolyte can be circulated in their respective compartments, which makes it possible t o achieve better results.

Finally, spacers, for example woven fabrics or grids, can be provided between the. electrodes and the separating diaphragm. I

The following examples, which are given without implying a limitation, illustrate the invention and show how it can be put into practice.

The commercial oxalic acid used in the examples is an acid prepared according to the techniques described in French Pat. No. 331,498 and British Pat. No. 1 1,487/1915; the various reactions carried out give an oxalic acid solution which is dried in vacuo and then drained it is an oxalic acid dihydra'te with a degree of purity of about 99.2%.

EXAMPLES l to 9 A series of experiments involving the reduction of oxalic acid is carried out; these various experiments differ from one another in the nature of the adjuvant used. The electrolytic cell in which these experiments are carried out possesses the following characteristics:

the two electrodes are rectangular lead plates,

the useful surface area of these electrodes is 0.8 dm

the cation exchange membrane is of the heterogeneous type, consisting of a crosslinked sulphonated styrene/divinylbenzene copolymer, dispersed in a polyvinyl chloride matrix, and is reinforced with a screen in the form of a woven fabric.

Permeation selectivity measured in 0.6 M KCl solution: 77.5%.

Substitution resistance measured in 0.6 M KCl solution: 7 ohms.cm

6 catholyte introduced initially: 2 l of an 8% strength by weight aqueous solution of oxalic acid (commercial oxalic acid). t

This solution is electrolysed continuously.

Distance from electrode to membrane: 3 mm. After 1 hour, 25 g of commercial oxalic acid are Two pumps cause the catholyte and the anolyte to added to the catholyte, followed by 25 g of this same flow in the corresponding compartments of the cell. acid every half hour. v The circuits where the anolyte and the catholyte flow During this entire period, the hydrogen evolved each contain an expansion vessel equipped with feed collected over a water trough and the change in the' and discharge pipelines. current yield which this evolution of hydrogen repre- The circuit of the catholyte also contains a heat exsents is followed. When this yield reaches a value hechanger. tween 6 and 12%, the particular adjuvant for each The electrolysis conditions are as follows: experiment is added to the catholyte. The volume of current density: 25 A/dm hydrogen evolved during the hour which follows the voltage: about 5.25 V addition of the adjuvant is measured, and the corretemperature: C sponding current yield is calculated. The results obrate of flow of the electrolytes over the electrodes: 1 tained with the various adjuvants which follow are m/second given in the tables below:

TABLE No. l

EXAM- Nature of the adjuvant Duration of Instantaneous Concentration. Average PLE electrolysis current yield in mM/l, of current before the (in corresthe adjuvant yield (in addition of ponding to the in the cathoduring the the adjuvant production of lyte at the hour follow- H2 at the time time of its ing the of the addition addition addition of of the adjuvant the adjuvant l NCH C H 2 hrs. 15 mins. 8 l 1.5 2 (CH N-LCH O-(CH F 2 hrs. 20 mins. 8.4 s 5.1

M -M2 CH3 CH -C H 3 CH3-N 5 hrs. 48 mins. 12 l 3.2

69 H 37 CH3 /C6H5 4 CHQ N 3 hrs. 20 mins. 6 2.8 3.9

CH.1\ fa s 5 CH37JQ 3 hrs. 20 mins. 8.9 4 4.7

C H orfi) In this table and in the following table, mM is the abbreviation for millimol.

TABLE No. 2 I

EXAM- Nature of the adjuvant Duration of Instantaneous Concentration. Average PLE electrolysis current yield in mM/l, of current before the (in corresthe adjuvant yield (in addition-of ponding to the in the cathoduring the the adjuvant production of lyte at the hour follow- H, at the time time of its ing the of the addition addition addition of of the adjuvant the adjuvant cH c n 6 CH N9 mins. 6.4 5 2.6

c n on 7 (C-,H,,),,N ,-(CH,) I-@(C H 5 hrs. 11 l a CH,CH2\ 8 nC H \CH CH l\ nC l -l 2 hrs. 18 mins. 9.5 5 6.5

26 CH,--CH,

ri -CH 9 3 hrs. l7 mins. 7.2 l 1.5

,b. ditertiary diamines of the: general formula N' .R"T m I").

ci q uaternary ammonium salts of the general formula and d. quaternary ammonium salts of the general formula sent a single saturated alkylene or oxydialkylene radical, or R R and'R can each representan-= R ,',R, ;:R and R each represent a linearor branched, saturated or unsaturated, aliphatic hydrocarbon radical, or an aliphatic radical containing at'leas'tone oxyalkylene links,.or,twoof R R, .R 'and;R' together form a single saturated alkylene o'r oxydialkylene radica l,.

at least' one of R -R R and R being a rnonova-,-

. lentgaromativhydrocarbon radical which is either .purely aromatic, or arylaliphatic, or atomatic and having as substituents saturatedorunSaturated, linear or branched, aliphatic radicals, the total number of carbon atoms in R R R and R being more than 15 and less than R R R R R and R are asdefined for R R R and R and R isas: defined for R the total number of carbon atoms in R R R R R R and R being morethan i3 andless than 40; yis equal to 1 2m 3,and A v A" is hydroxy or an anion such that AH represents an inorganic or organic acid. 2. Process according to clairn 1 wherein at least one of R10, R119 R12! R13, R14 151' 16v R18, R19 R20! 2 b R22 R R R R and R is an aliphatic radical of formula DH 2)n]m 0H wheren=2 or3 andm= l to [0.

3.-Process according to claim 1 wherein at least one of R R and-R is an arylaliphatic radical of formula C l-i 4 R where R9 is a linear or branched saturated or -unsa'turated aliphatic divalent hydrocarbon radical. I, v

4. Process according to claim 1 wherein the adjuvant is used at a concentration at which it is soluble in water.

5. Process according to claim 1 wherein the adjuvant is selected from tribenzylamine; (dimethylamino)-ethyl ether; dimethyl-benzyl-dodecyl-ammonium,. diethylbenzyl-dodecyl-ammonium, dimethyl-benzyl-tetradecyl-ammonium, diethyl-benzyl-tetradecyl-ammonium, dimethyl-benzyl-hexadecyl-ammonium, diethyl-benzylhexadecyl-amm'onium, dimethyl-benzyl-octadecyl ammonium," diethyl-benzyl-octadecyl-ammonium, di-

' methyl-benzyl-eicosyl-ammonium,diethyl-benzyl-eico aliphatic radical containing atlileast one oxyalkylene link, at least one of the radicals R R and-R 1 being an arylaliphatic radical, theradicals R R and. R together having less-than 40-carbon atoms,

R R R arid R each .represent linear or branched saturated-or unsaturated aliphatic hydrocarbon radicals, or an aliphatic radical containing I l,4-diazoniadicyclo[2,2,2]octane syl-ammonium, dimethy]-benzyl-docosyl-ammonium H and diethyl-benzyl-docosyl-ammonium hydroxides and salts; dimethyl:phenyl-dodecyhammonium and dimethyl-phenyI hexadecyl-ammonium hydroxides and salts; and l,6-(triethylammonio)-hexane, l,4-di-(n-butyl)- and l ,4-di-(ndodecyl)- l ,4-diazoniadicyclo[2,2,21octane hydroxides and salts. Y

6. A process according to claim 1 wherein the salt is v a halide."

at least one oxyalkylene links or at least one of R 7.'A process according to claim 1 wherein the concentration of adjuvant in' the catholyte is 0.0001 to 0.5% w/w. i

8. A process according to claim 1 wherein the temperature in the catholyte is 5-35C. 9. A process according to claim 1 wherein the currentdensity is 10-35 Amps/dm.

.10....Alfprdces's according to anyone of the preceding claims wherein theseparating diaphragm is a cation exchange membrane. 

1. PROCESS FOR THE PREPARATION OF GLYOXYLIC ACID BY CATHODIC REDUCTION OF OXALIC ACID, BY CARRYING OUT AN ELECTROLYSIS IN AN ELCTROLYSER COMPRISING A CATHODE, A CATHODE COMPARTMENT, A SEPARATING DIAPHRAGM, AN ANODE AND AN ANODE COMPARTMENT WHEREIN THE SAID CATHODE COMPARTMENT CONTAINS A CATHOLYTE CONSISTING ESSENTIALLY OF AN AQUEOUS SOLUTION OF OXALIX ACID AND 0.00005 TO 1% W/W OF AN ADJUVANT CHOSEN FROM: A. TERTIARY AMINES OF THE GENERAL FORMULA
 2. Process according to claim 1 wherein at least one of R10, R11, R12, R13, R14, R15, R16, R18, R19, R20, R21, R22, R23, R24, R25, R26, and R27 is an aliphatic radical of formula - (CH2)n - (O - (CH2)n)m OH where n 2 or 3 and m 1 to
 10. 3. Process according to claim 1 wherein at least one of R10, R11 and R12 is an arylaliphatic radical of formula C6H5 - R9 - where R9 is a linear or branched saturated or unsaturated aliphatic divalent hydrocarbon radical.
 4. Process according to claim 1 wherein the adjuvant is used at a concentration at which it is soluble in water.
 5. Process according to claim 1 wherein the adjuvant is selected from tribenzylamine; (dimethylamino)-ethyl ether; dimethyl-benzyl-dodecyl-ammonium, diethyl-benzyl-dodecyl-ammonium, dimethyl-benzyl-tetradecyl-ammonium, diethYl-benzyl-tetradecyl-ammonium, dimethyl-benzyl-hexadecyl-ammonium, diethyl-benzyl-hexadecyl-ammonium, dimethyl-benzyl-octadecyl-ammonium, diethyl-benzyl-octadecyl-ammonium, dimethyl-benzyl-eicosyl-ammonium, diethyl-benzyl-eicosyl-ammonium, dimethyl-benzyl-docosyl-ammonium and diethyl-benzyl-docosyl-ammonium hydroxides and salts; dimethyl-phenyl-dodecyl-ammonium and dimethyl-phenyl-hexadecyl-ammonium hydroxides and salts; and 1,6-(triethylammonio)-hexane, 1,4-di-(n-butyl)-1,4-diazoniadicyclo(2,2,2)octane and 1,4-di-(n-dodecyl)-1,4-diazoniadicyclo(2,2,2)octane hydroxides and salts.
 6. A process according to claim 1 wherein the salt is a halide.
 7. A process according to claim 1 wherein the concentration of adjuvant in the catholyte is 0.0001 to 0.5% w/w.
 8. A process according to claim 1 wherein the temperature in the catholyte is 5*-35*C.
 9. A process according to claim 1 wherein the current density is 10-35 Amps/dm2.
 10. A process according to any one of the preceding claims wherein the separating diaphragm is a cation exchange membrane. 